Plastic pipe is generally formed by extruding plastic into a mold tunnel. The pipe is formed by either vacuum forming or blow molding. After the pipe has been shaped, it is typically cooled by cooling of the mold blocks. As the pipe continues down the mold tunnel the cooling becomes less and less efficient because the pipe shrinks producing an air gas between the mold blocks and the pipe. Accordingly, the pipe is insulated from and has difficulty in giving heat off to the mold blocks as the pipe continues down the mold tunnel.